Electric heater



April 4, 1961 M. K. MURPHY 2,978,568

' ELECTRIC HEATER Original Filed May 3, 1957 r/Z 55 E 2 /6 PM [32 M (if(Z4, My

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United States Patent ELECTRIC HEATER Maxwell K. Murphy, 535 W.Goldengate, Detroit, Mich.

Continuation of application Ser. No. 656,900, May 3, 1957. Thisapplication Nov. 3, 1958, Ser. No. 771,604

12 Claims. (Cl. 219-39) This invention relates to electrical spaceheaters and space heating systems and particularly to an improvedcombination radiant and convection heater, and to improved controls forsuch a heater.

This application is a continuation of my co-pending application SerialNo. 656,900, filed May 3, 1957, now abandoned.

The benefits and advantages of radiant space heating have beenrecognized for some time, and the added convenience of electricalradiant heating has led to widespread adoption of wall mounted heatersutilizing glass heater elements. These glass heater elements have anelectrical resistance grid fused on one surface thereof and areextremely eificient radiators of infra-red heat rays. Recently vitreouscoated metal plates with a resistance grid fused on one of the coatedsurfaces have been used instead of the glass plates.

One objection to radiant heaters of the type mentioned is that theirheating effect is slow in manifesting itself when the heaters arestarted from the cold state, and because most of the heating effect isradiant with only a small amount of convection, portions of the heatedspace not directly in the path of the heat rays sometimes remain coldand uncomfortable.

The principal object of my invention is to provide an improvedcombination radiant and convection heater which provides all of theadvantages of true radiant heating and, in addition, provides convectionheat circulated by a fan when fast warm-up is desired and when areas notin the direct path of the radiant rays are to be heated.

The accompanying drawing shows a preferred form of my invention andreference numerals designate parts thereon referred to in the followingdescription.

In the drawing:

Fig. l is a front elevation of a wall heater embodying my invention;

Fig. 2 is a vertical section on an enlarged scale taken on the line 2-2of Fig. 1;

Fig. 3 is a horizontal section on an enlarged scale taken on the line3-3 of Fig. 1; and' Fig. 4 is a schematic wiring diagram of the heatercontrol.

Referring to the drawing, it may be seen that my improved heatercomprises a casing of metal, Fiberglas or other suitable material. Thecasing has back, side, top and bottom walls as shown, and is providedwith an air intake 12 and an air outlet 14. A front wall 16 is recessedas shown to accommodate a radiant heating element 18 which is mounted onthe front wall by means of the brackets 20 and screws 22.

The element 18 may be of glass type such as that shown in Glynn PatentNumber 2,622,178 (in which event mounting means suitable for supportingglass must be used) but preferably is of the metal type. Referring toFig. 3, it may be seen that the element comprises a metal sheet 24coated on both surfaces with vitreous enamel 26. A metallic resistancegrid 28 is adhered to one vitreous surface preferably by spraying whilethe metal is in molten state, and a protective coating 30 of siliconevarnish or the like is applied to the surface carrying the resistor.

Application of a voltage across the resistor grid 28 will heat the paneland heat rays, the majority of which are in the infra-red range, will beradiated from the front surface of the panel. The recessed wall 16 ispreferably polished such that it acts as a reflector and thus increasesthe radiant effect of the element by reflecting heat radiated from therear surface which carries the resistor.

The element 18 is spaced from the reflector wall 16 and clearance isprovided around all four marginal edges of the element therebypermitting convection air currents to enter the slot at the bottom ofthe element and to circulate upwardly of the space between the wall 16and element 18 and out through the slot at the top of the element.

In the chamber 32 behind the wall 16, a second heating element 34 ismounted by means of brackets 36 or other suitable means. The element 34is preferably identical with element 18, but other types of heatingelements may be used inasmuch as the element 34 supplies no radiant heatdirectly to the room, but only convection heat.

A fan assembly 38 which includes a motor 40 and a bladed rotor 42 ismounted in the top portion of the easing as shown. A baflle 44 ismounted in the bottom portion of the casing and serves to direct airpropelled downwardly through the chamber 32 outwardly through the outletregister 14.

The heater is adapted for automatic control by means of a thermostat Tas shown by the schematic diagram of Fig. 4. As indicated, line voltageis connected to the element 18 through a relay actuated switch 46. Linevoltage is similarly connected to element 34 by a relay actuated switch48 which also controls the motor of fan 38. A transformer 50 suppliesrelay coils 52 and 54 under control of the thermostat T. Any suitable,commercially obtainable type of thermostat and switches may be used. Itis preferred, however, that the thermostat be of the differential typeso that the switches 46, 48, may be opened and closed at the same ordifferent temperatures.

The heater operates as follows:

Let it be assumed that both switches 46 and 48 are open, the temperatureof the room or other space to be heated is below that desired forcomfort, say 70 F., that the thermostat T is set to close the switch 46whenever the room temperature drops below 74 F., and to close the switch48 whenever the room temperature drops below 70 F.

Both switches 46 and 48 will close through action of the relays 52 and54, and the elements 18 and 34 as well as the fan 38 will be energized.Element 18 will, as soon as it warms to radiating temperature, emit heatrays which will intersect objects in their path causing warmth.Convection currents of air will enter the slot below the element 18 andwill emerge as warmed air through the slot at the top of the element andwill circulate about the room.

At the same time, air drawn in through the inlet 12 from the upperportion of the room by the fan blades 42 will pass downwardly of thechamber 32 on both sides of the element 34 and after being thus heatedwill pass outwardly through the register 14 and circulate around theroom with considerable velocity.

This dual effect of radiant and convection heat will quickly warm theroom. When the temperature of the room rises to 70 F. (or some othertemperature as set by the operator), switch 48 will open and cut off thepower to the element 34 and the fan 38. Element 18 will continue to emitheat rays until the room temperature reaches 74' F., or some otherdesired value, and then switch 46 will open cutting off power to theelement. Under normal conditions, switch 46 will cycle on and offthereby causing element 18 to be alternately energized and deenergizedin accordance with the conditions prevailing.

It is characteristic of the type of heating element disclosed that heatis retained in the element for a comparatively long period when currentis off and thus the element will continue to radiate during an oifperiod of considerable length. It is recommended that the thermostat Tbe located somewhere in the room remote from the heater and not in thedirect path of the emitted rays from element 18. Correct adjustment ofthe heater and of the thermostat setting will cause the room to beheated entirely by the radiant element 18, after the room has beenwarmed up, which is the most satisfactory as well as the most economicalmethod of heating.

A drop in temperature, sudden or otherwise, to a value below the settingof relay 54 will cause energization of element 54 and fan 38, and bothradiant and forced air convection heat will be available.

The width and depth of the heater are preferably chosen such that theentire assembly will fit flush with a wall surface between joists, whichare usually 16 inches apart. The height can be chosen to present apleasing appearance and in large rooms two or more units controlled byone or more thermostats may be used. In some instances where heat isdesired in adjoining rooms or closets from one heater, a second registermay be provided in the back wall of the casing opposite the register 14and the bafile 44 eliminated or modified to provide airflow in oppositedirections.

It will thus be seen that I have provided an improved electric heaterwhich is compact, easily constructed and economical in construction, andwhich provides the advantages of both radiant heating and forced airconvection heating with economy of operation and flexibility of control.

While I have shown and described a specific form of my invention, itwill be understood that I have done so for illustrative purposes onlyand I do not intend to limit the scope of the invention except as setforth in the appended claims.

I claim:

1. A combined radiant and convectionspace heater comprising incombination, an upright casing, an electrical radiant heating panelmounted on the front of said casing and spaced from said casing toprovide for circulation of convection air currents between said casingand said panel, a chamber within the casing, an electrical convectionheating element in said chamber, blower means disposed in the upperportion of said casing for forcing air downwardly thereof, an air outletin the lower portion of said chamber, and means operable automaticallyin response to temperature conditions in the heated space to energizesaid heating elements selectively.

2. A combined radiant and convection space heater comprising incombination, a casing having an air inlet, an air outlet and means forforcing an airstream downwardly through said casing, a front wall onsaid casing, a sheet type radiant heating element mounted on said frontwall in spaced relationship therewith, slots at the top and bottom edgesof said element providing means for circulation of convection aircurrents in the space between said wall and said element, said wallbeing polished to provide reflection of heat rays radiated from the backof said element, and a second heating element disposed in said casing inthe path of said airstream.

3. A combined radiant and convection space heater comprising incombination, a casing having an air inlet, an air outlet and means forforcing an airstream through said'casing, a front wall on said casing, aradiant heating element of sheet form mounted on said front wall inspaced relation thereto, slots adjacent the top and bottom of saidelement permitting air to enter and travel upwardly of said element andout over the top of said element, a second heating element disposed insaid casing in the path of said airstream, said forced airstreamentering at the top and leaving at the bottom of said casing.

4. A combined radiant and convection heating arrangement comprising incombination, an upright casing having a chamber therein and a frontwall, an air inlet in the upper portion of said chamber, an air outletin the bottom portion of said chamber, an electrical heating elementmounted in said casing in spaced relation to the walls thereof, blowermeans for circulating air from said inlet over said element and outthrough said outlet, an electrical radiant heating element mounted onsaid front wall in'spaced relation thereto, slots adjacent the top andbottom of said radiant element permitting circulation of convection aircurrents upwardly thereof, the direction of said currents being oppositeto the direction of the air currents in said chamber.

5. A combined radiant and convection heating arrangement comprising incombination, an upright casing having a-chamber therein and a frontwall, an air inlet in the upper portion of said chamber, an air outletin the bottom portion of said chamber, and electrical heating elementmounted in said casing in spaced relation to the walls thereof, blowermeans for circulating air from said inlet over said element and outthrough said outlet, an electrical radiant heating element mounted onsaid front wall in spaced relation thereto, slots adjacent the top andbottom of said radiant element permitting circulation of convection aircurrents upwardly thereof, electrically actuated means for energizingand deenergizing said elements and means operably associated with saidelectrically actuated means for energizing said blower when said firstheating element is energized.

6. A combined radiant and convection heating arrangement comprising incombination, an upright casing having a chamber therein and a frontwall, an air inlet in the upper portion of said chamber, an outlet inthe bottom portion of said chamber, an electrical heating elementmounted in said casing in spaced relation to the walls thereof, blowermeans for circulating air from said inlet over said element and outthrough said outlet, an electrical radiant heating element mounted onsaid front wall in spaced relation thereto, slots adjacent the top andbottom of said radiant element permitting circulation of convection aircurrents upwardly thereof, differential thermostat means for causingenergization of said heating elements in response to temperatureconditions in the heated space, said means being constructed andarranged to energize said radiant heating element at a preselectedtemperature and to energize said other heating element at a lowerpreselected temperature.

7. A combined radiant and convection heating system comprising incombination, an upright casing having a chamber therein and a frontWall, an air inlet in the upper portion of said chamber, an air outletin the bot tom portion of said chamber, an electrical heating ele mentmounted in said casing in spaced relation to the walls thereof, blowermeans for circulating air from said inlet over said element and outthrough said outlet. an electrical radiant heating element mounted onsaid front wall, differential thermostat means for causing energizationof said heating elements in response to temperature conditions in theheated space, said means being constructed and arranged to energize saidradiant heating element at a preselected temperature and to energizesaid other heating element at a lower preselected temperature.

8. In a space heating system in combination, an electrical convectionheating element, means for circulating air over said convection heatingelement and to the heated space for heating said space by convection, anelectrical radiant heating element, thermostat means for causingenergization of said heating elements in response to temperatureconditions in the heated space, said thermostat means being constructedand arranged to energize both of said heating elements at a preselectedtemperature and to deenergize said convection heating element only at apreselected higher temperature.

9. In a space heating system in combination, an electrical convectionheating element, means for circulating air over said convection heatingelement and to the heated space for heating said space by convection, anelectrical radiant heating element, thermostat means for causingenergization of said heating elements in response to temperatureconditions in the heated space, said thermostat means being constructedand arranged to energize both of said heating elements at a preselectedtemperature, to deenergize said convection heating element at a firstpreselected higher temperature and to deenergize said radiant heatingelement at a second preselected higher temperature higher than saidfirst preselected higher temperature.

10. In a space heating system in combination, an electrical convectionheating element, means for circulating air over said convection heatingelement and to the heated space for heating said space by convection, anelectrical radiant heating element, theremostat means for causingenergization of said heating elements in response to temperatureconditions in the heated space, said thermostat means being constructedand arranged to energize both of said heating elements at a preselectedtemperature, to deenergize said convection heating element when thetemperature of the heated space reaches a preselected highertemperature, and to deenergize said radiant heating element when thetemperature of the heated space reaches a second preselected highertemperature.

11. In a space heating system in combination, an electrical convectionheating element, means for circulating air over said convection heatingelement and to the heated space for heating said space by convection, anelectrical radiant heating element, thermostat means for causingenergization of said heating elements in response to temperatureconditions in the heated space, said thermostat means being constructedand arranged to energize and deenergize both of said heating elements atpreselected temperatures, said radiant heating element being energizedand deenergized at preselected higher tempera tures respectively thansaid convection heating element.

12. In a space heating system in combination, an electrical convectionheating element, means for circulating air over said convection heatingelement and to the heated space for heating said space by convection, anelectrical radiant heating element, thermostat means for causingenergization of said heating elements in response to temperatureconditions in the heated space, said thermostat means being constructedand arranged to energize and deenergize both of said heating elements atpreselected temperatures, said convection heating element beingenergized and deenergized at preselected lower temperatures respectivelythan said radiant heating element.

References Cited in the file of this patent UNITED STATES PATENTS1,422,130 Reynolds July 11, 1922 1,652,686 Schoenfeld Dec. 13, 19271,705,769 Kercher et al Mar. 19, 1929 1,910,105 Herring May 23, 19331,922,220 Sprague Aug. 15, 1933 1,986,350 Logan Jan. 1, 1935 2,065,760Smith Dec. 29, 1936 2,471,784 Seifner May 31, 1949 2,707,745 Farr et a1May 3, 1955 2,781,440 Petersen et a1 Feb. 12, 1957 2,827,540 UnderwoodMar. 18, 1958 FOREIGN PATENTS 207,954 Australia May 15, 1957 486,711Italy Nov. 17, 1953

